Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$196.50	10.283%	$216.7061	$216.71	$216.70	$216.70
Purchase #2	$244.30	10.857%	$270.8237	$270.82	$270.80	$270.80
Purchase #3	$23.35	4.110%	$24.3097	$24.31	$24.30	$24.30
Purchase #4	$241.93	10.856%	$268.1939	$268.19	$268.20	$268.20
Purchase #5	$112.43	9.406%	$123.0052	$123.01	$123.00	$123.00
Purchase #6	$186.72	12.859%	$210.7303	$210.73	$210.75	$210.70
Purchase #7	$12.33	10.215%	$13.5895	$13.59	$13.60	$13.60
7 purchase totals =	$1,017.56		$1,127.3584	$1,127.36	$1,127.35	$1,127.30